Poxviruses are complex DNA viruses which exhibit an unusual degree of genetic and physical autonomy from the host cell. Infection is restricted to the cytoplasm of the infected cell, and the vast majority of the proteins involved in viral gene expression, genome replication, and morphogenesis are encoded within the 192 kb viral genome. Moreover, the genome encodes a large repertoire of proteins which intersect with and manipulate the host's immune, inflammatory and anti-viral responses. This unusual combination - in which the basic life cycle is dominated by viral genes and so can be studied with genetic precision, but infection is intimately associated with a broad spectrum of virus/host interactions - makes these viruses intriguing and fruitful systems for state-of-the-art research. The importance of poxviruses in biomedical history is illustrated by the successful use of vaccinia virus in the worldwide vaccination campaign that eradicated smallpox as a human threat. Today, recombinant poxviruses are being designed as multivalent vaccines for both medical and veterinary purposes. The emergence of Molluscum contagiosum, another poxvirus, as a major opportunistic infection of AIDS patients underscores the continuing relevance of these viruses to human disease. The International Poxvirus Symposia are held biannually and are the premier forum for presentation and discussion of poxvirus research. The 1998 meeting is the XIIth Poxvirus Symposium, and should prove as stimulating and informative as previous conferences. We expect to have seventy to eighty oral presentations in eight scientific sessions, and eighty poster presentations in two additional scientific sessions. All presenters will be chosen from those submitting Abstracts. This approach will facilitate the presentation of the most recent and exciting results, and should increase participation by young investigators, post-doctoral fellows and graduate students. Based on previous conferences, we anticipate that approximately 175 scientists will attend.